An electrochemical sensor can be used for various applications, such as for sensing the presence of one or more constituent gases, such as oxygen, carbon monoxide, etc., in an environment around the electrochemical sensor. The electrochemical sensor can include a counter electrode (CE), a reference electrode (RE), and a sensing electrode (SE). The sensing electrode can also be referred to as a working electrode (WE). The electrochemical sensor can include one or more sensor characteristics, such as impedance, which can provide an indication of how effectively the sensor is still operating, such as by comparing a sensor characteristic to a specified reference value. This can help determine whether or when to replace a failing electrochemical sensor, or to determine how much useful life can be expected from the electrochemical sensor before replacement.